Surgery exact triangles in various 3-manifold Floer homology theories provide an important tool in studying and computing the relevant Floer homology groups. These exact triangles relate the invariants of 3-manifolds, obtained by three different Dehn surgeries on a fixed knot. In this paper, the behavior of SUpN q-instanton Floer homology with respect to Dehn surgery is studied. In particular, it is shown that there are surgery exact tetragons and pentagons, respectively, for SUp3qand SUp4qinstanton Floer homologies. It is also conjectured that SUpN q-instanton Floer homology in general admits a surgery exact pN`1q-gon. An essential step in the proof is the construction of a family of asymptotically cylindrical metrics on ALE spaces of type A n . This family is parametrized by the pn´2q-dimensional associahedron and consists of anti-self-dual metrics with positive scalar curvature. The metrics in the family also admit a torus symmetry.
Homological Algebra of the Surgery PolygonIn this section, we define exact n-gons and exact n-cubes. It is shown in Subsection 2.2 that any exact ncube induces an exact pn`1q-gon. We shall obtain the exact pN`1q-gon of Theorem 1.6 by constructing an exact N -cube and then applying this algebraic construction.